Electromagnetic oscillatory drive



March 1965 w. R. BAUMGARTNER 3,176,171

ELECTROMAGNETIC OSCILLATOR! DRIVE Filed March 9, 1962 United States Patent 3,176,171 ELECTROMAGNETIC OSCILLATORY DRIVE Werner Richard Baumgartner, Neuchatel, Switzerland,

assignor to Laboratoire Suisse de Recherches Horlogeres, Nenchatei, Switzerland, 2 Swiss company Filed Mar. 9, 1962, Ser. No. 178,711 Claims priority, application Switzerland, Mar. 14, 1961, 3,083/ 61 2 Claims. (Cl. 310-38) Conventional electronic time-pieces are generally provided with a circuit including a control winding and a driving winding which are inserted respectively in the control circuit and in the power circuit of a transistor amplifier. The movement of an oscillating part such as a spiral balance spring or a tuning fork produces a pulse in the control winding which renders the transistor conductive. The latter allows a pulse to pass through it and into the driving winding, the flux produced by which provides for the acceleration of the oscillating part.

My invention has for its object a novel arrangement of said type, the novelty of which consists in that the control and driving windings are carried by the same ferromagnetic armature the ends of which are spaced by a very narrow gap and face one of the poles of a magnetic system. This pole oscillates in front of the gap, either the armature or the magnetic system being rigid with the oscillator.

The accompanying drawing illustrates, by way of example, an advantageous embodiment of my invention. In the drawing:

FIG. 1 is a general plan view of the oscillator and time-piece mechanism,

FIGS. 2 and 3 are cross-sectional views taken on lines IIII and IIIIII respectively of FIG. 1,

FIG. 4 is a wiring diagram and FIG. 5 is a graph showing the voltages induced in the windings illustrated in FIG. 4.

The electronic wiring diagram FIG. 4, of the time-piece illustrated includes a supply of current 1 constituted by a voltaic battery or a storage battery. A transistor 2 including in its control circuit an R-C circuit and a control winding 3 and in its power circuit a driving winding 4 are connected to the battery. These two windings are carried by an armature 5 (FIG. 3) of which two ends 5a and 5b form between them a very narrow gap 6 of a magnitude of about 0.1 mm. The armature may be made of ferrite or of the alloy sold under the trademark Permalloy for instance. In the latter case, it is constituted by superposed sheets insulated with reference to one another so as to reduce the eddy currents.

A magnetic system 7 is adapted to oscillate in front of the gap 6 separating it from the armature 5 under the action of a torsion oscillator carrying the system as hereafter described. The oscillator comprises a torsion spring 8 having a V-shaped cross-section and fitted at both ends in the time-piece plate. The torsion spring carries a transverse arm 9 to one end of which the magnetic system 7 is secured while its other end carries a catch mechanism which is not illustrated. The catch mechanism drives a ratchet wheel 10 rigid with a worm 11 which drives in its turn the watch mechanism which includes an intermediate gear 12, an eccentric seconds gear 13, a third gear 14 and lastly a center gear 15. The motion work controlling the hour hand is not illustrated.

The magnetic system 7 is constituted by a rectilinear magnetized bar 16 fitted inside a mild U-shaped ferromagnetic member 17 the arms of which extend to either side of the bar a short distance from the corresponding surfaces of the latter. The space between the bar and member may be filled with air or the like non-magnetic 3,176,171 Patented Mar. 30, 1965 material and should be designed so as to provide an optimum magnetic energy in proximity with the ends 5a and 5b of the armature for a predetermined magnetic system. Furthermore, the member 17 reduces to a maximum the outer field produced by the magnet and cuts out therefor the major part of the losses produced by eddy currents. When in operation the oscillating magnetized bar first moves towards the end 5:! of the armature and applies torsion to the spring 8 and it induces a voltage Vi of a very short duration in the control winding 3. Then the magnetized bar is restored by the spring towards the opposite end 5b of the armature and at the moment at which the bar faces the gap 6, that is when the oscillating system is in its inoperative position or condition, the transistor which has been rendered conductive by the control voltage pulse applied by the control winding 3 allows a driving pulse Vm to pass through the driving winding 4. The flux produced, provides an acceleration of the bar towards the end 5b. The impulse may be given slightly ahead of this inoperative position so as to correct the possible error isochronism ascribable to the holding fast in position of the ends of the spring 8.

As shown in FIG. 5 the oscillating mechanism produces pulses alternately in the control winding 3 and driving winding 4. The control pulses in the control winding have a voltage Vi value in the order of 0.4 millivolt and are applied spaced about twenty milliseconds, shown or the abscissa of the graph, apart from the drive voltage, Vm, pulses produced in the driving winding which have about twice the peak value of the control pulses in the control winding since these pulses must work against the force of the torsion spring 8. The alternate control and driving pulses maintain the oscillations of the system and are in turn induced by the oscillations once the oscillations are started.

It is possible to obtain, with this arrangement, an oscillation at a frequency ranging between about 30 and 50 cycles whereas in the case of arrangements provided with a tuning fork, the frequency is much higher since it reaches about 500 cycles. By resorting to a narrow gap and providing a suflicient concentration of the flux in the magnetized bar, it is possible to obtain extremely short control pulses in the control winding 3 which allows maintaining the oscillation through pulses of very short duration. The efliciency of the arrangement is excellent chiefly because the pulses are applied to the magnetized bar at moments at which the oscillating means pass through their inoperative position of equilibrium and also by reason of the reduced losses due to a considerable reduction of eddy currents. The adjustment of operation is obtained through a shifting of the magnetic system towards and away from the gap in the armature. This is accomplished by adjusting the axial position of the armature 5 with an adjusting screw 20 having one end anchored in the armature and passing through a threaded hole in a mount 21.

What I claim is:

1. An oscillatory motor for controlling an electronic time-piece comprising, an electronic circuit for energizing said motor including a driving winding and a control winding, a U-shaped ferromagnetic core including two legs carrying respectively said driving winding and said control winding, the free terminal surfaces of which are separated by a very narrow gap of about 0.1 mm., at a small distance therefrom, a magnet bar, the longitudinal axis of said bar extending perpendicularly to the terminal surfaces of the core legs and passing normally through the middle of said gap to oscillate in front of the gap under the action of the cooperating electronic circuit, and a U-shaped armature including two legs extending symmetrically to either side of said magnet bar, in par- 3 allelisrn therewith in the plane including the longitudinal axes of the core legs.

2. An oscillatory motor for controlling an electronic time-piece comprising, an electronic circuit energizing said motor including a driving winding and a control winding, comprising a U-shaped ferromagnetic core including two legs carrying respectively said driving winding and said control winding, the free terminal surfaces of which are separated by a very narrow gap of about 0.1 mm., a magnet bar one end of which faces said free terminal surfaces at a small distance therefrom, the axis of said bar extending perpendicularly to the terminal surfaces of the core legs and passing normally through the middle of said gap to oscillate in front of the gap under the action of the cooperating electronic circuit, a U-shaped armature stationary with reference to the core, including two legs extending symmetrically to either side of said magnet bar, in parallelism therewith in the plane including the longitudinal axes of the core legs, and means for adjusting the distance between the end of the magnet bar facing the gap and the terminal surfaces of the core legs.

References Cited by the Examiner UNITED STATES PATENTS MILTON O. HIRSHFIELD, Primary Examiner.

JOSEPH P. STRIZAK, Examiner. 

1. AN OSCILLATORY MOTOR FOR CONTROLLING AN ELECTRONIC TIME-PIECE COMPRISING, AN ELECTRONIC CIRCUIT FOR ENERGIZING SAID MOTOR INCLUDING A DRIVING WINDING AND A CONTROL WINDING, A U-SHAPED FERROMAGNETIC CORE INCLUDING TWO LEGS CARRYING RESPECTIVELY SAID DRIVING WINDING AND SAID CONTROL WINDING, THE FREE TERMINAL SURFACES OF WHICH ARE SEPARATED BY A VERY NARROW GAP OF ABOUT 0.1 MM., AT A SMALL DISTANCE THEREFROM, A MAGNET BAR, THE LONGITUDINAL AXIS OF SAID BAR EXTENDING PERPENDICULARLY TO THE TERMINAL SURFACES OF THE CORE LEGS AND PASSING NORMALLY THROUGH THE MIDDLE OF SAID GAP TO OSCILLATE IN FRONT OF THE GAP UNDER THE ACTION OF THE COOPERATING ELECTRONIC CIRCUIT, AND A U-SHAPED ARMATURE, INCLUDING TWO LEGS EXTENDING SYMMETRICALLY TO EITHER SIDE OF SAID MAGNET BAR, IN PARALLELISM THEREWITH IN THE PLANE INCLUDING THE LONGITUDINAL AXES OF THE CORE LEGS. 